It's in need of a sharpener, silly! (9)
I believe the answer is:
pointless
'silly' is the definition.
(I've seen this before)
'it's in need of a sharpener' is the wordplay.
I cannot really understand how this works, but
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is located in the answer.
'in' is present in the answer.
'of' could be 'o' and 'o' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for pointless that I've seen before include "Futile, irrelevant" , "no avail" , "Quite vain" , "Ineffectual" , "Futile - TV quiz show" .)